Ditching My 4S LiPos for 5S

I recently started flying my quads on 5S LiPo batteries, and it has been an awesome upgrade. Until recently, I didn’t have enough 5S packs to spend an entire afternoon flying. I only had five 5S batteries, so I’d always end up flying a few 4S packs every time I went to the park.

That changed when I acquired a big, heavy 10,000 mAh 6S battery for field charging. I’m no longer limited to five 5S batteries. Now I’m carrying enough capacity to charge a dozen of my 1300 mAh 5S packs, and I can parallel charge six of those packs in about 23 minutes.

Last night, I pulled all the 4S packs out of my giant quadcopter backpack, and I ordered a few more 1300 mAh 5S batteries from chinahobbyline.com.

When I fly a 1500 mAh 4S with a GoPro Session mounted to my quad, I lose quite a bit of flight time. Without the GoPro, I can often approach five minutes of flight time. Strap a GoPro to the roof, and I am lucky if I can hit three minutes. The extra weight of the GoPro is tolerable, but you can sure tell that it is there.

When I fly a 1300 mAh 5S, it doesn’t matter whether I have the GoPro or not. Most of my flights tend to last four to five minutes. I’m sure the weight of the GoPro is having an impact on my flight times. It can’t be by much, because I have plenty of flights at both ends of the range with and without the GoPro.

This is where my science is lacking. None of my flights are the same, and I fly with the GoPro more often than without—I only fly without the GoPro Session if I forget to bring it to the park.

Why 5S? Why not 6S?

Cost is my primary reason for choosing 5S. I can buy a 1300 mAh 5S LiPo for $25, and it will have more punch than the most expensive 4S pack. When I hammer the throttle, my cheap 5S pack sags to 3.2 volts per cell. That’s still 15.2 volts. You’ll have trouble finding a 4S LiPo that can keep the volts that high at full throttle!

I tried one of Brian’s 1400 mAh Tattu 6S batteries. The first minute of my flight was great. I was gently cruising around and blipping the throttle. The quad didn’t spin out of control or burst into flames—that’s usually good news!

Then I did a short punch out. It was oscillating quite a bit, but I’m sure some tuning of the TPA breakpoint would fix that. After I hit the top of the punch out, I began steering the quad to keep it away from the parking lot. That’s when I lost video.

I don’t know exactly what happened. The GoPro footage looks like there was a failsafe. The VTX definitely lost power. When it hit the ground, the video feed came back. I didn’t see the Betaflight logo, so I don’t think the flight controller rebooted. The impact knocked my GoPro Session mount off, and it rolled about 30 feet from the quad, so I didn’t get to hear whether the ESCs rebooted or not.

If I had to go back, I might have chosen the 2400 KV version of the F40 Pro motors. They’d be more appropriate for attempting 6S, and they’d still fly fine on 4S!

How fast is 5S?

It depends how you define fast. When I talk about fast, I’m almost always talking about acceleration. I don’t want a Buggati Veyron that can hit 250 MPH. I want a car that can hit 60 MPH in an insanely short amount of time—I can do that over and over again on a trip to the grocery store!

I feel the same way about my quads. I run Racekraft 5051 props. They have tons of bottom-end power, but they sure peter out at the top end. I brought the speed gun and some aggressive Avan biblade props to the field last weekend. I figured they’d have more top end than my Racekraft 5051 props.

Unfortunately, I couldn’t get my quad to fly well on the biblades. It was shaking and vibrating like crazy. I probably need to turn some filtering back on, but I didn’t have a laptop with me at the time. We didn’t want to waste the opportunity for a speed run, so I flew the 5051 props as fast as I knew how.

I only did two passes. The first pass was most likely the fastest, but we didn’t manage to get a reading on the speed gun. It was perfect. Brian says I was only about 8 feet from the ground the whole time, and I ran straight past him. It was a fresh 5S pack, and I managed to get it to sag all the way to 3.02 volts. That’s the most sag I’ve ever seen, so I must have been pushing it hard. The quad was only armed for five seconds when I was already past Brian and the speed gun!

The second pass wasn’t as well executed. I was flying less directly at the gun, I was gaining too much altitude, and I crashed right after the run. It felt like a failsafe—Brian says I must have outrun the radio signal!

The speed gun reading on that pass was 95 MPH. In my opinion, that is a respectable number for these stupidly aggressive props. I’m sure we’ll be trying some less aggressive, more aerodynamic props. I don’t think I’ll have any trouble breaking 100 MPH.

What is this talk about field charging?

In our local quad group, we’ve talked about field charging quite a bit. More often than not, we come to the same conclusion. We’d rather invest in more packs for the quads and do all our charging at home.

Our opinions have been changing, though. Most of us have upgraded from four-button chargers to ISDT Q6 Pro chargers. The ISDT chargers are fantastic for charging in the field, because they are small and powerful. I’ve plugged it into the car at the park several times.

It has been handy when new pilots are participating, and they don’t have enough batteries to fly all day. I’ve let new pilots use my batteries in the past, and I’ve had more than one of them come back smashed. If I charge their batteries, I don’t have to put my own at risk!

Several of us are now flying different battery voltages. We carry tiny 3S packs for our micro quads, 4S packs for [our older 5” quads][bf], and 5S or 6S for our newest quads. How many of each battery should you carry? Having a generous assortment of batteries will add a lot of weight to your bag.

Charging at the car is fine, but I’ve found that I can only push the charger to four or five amps with the cigarette lighter port in the bag. I know I can get more juice directly from the battery terminals, but that’s a much bigger hassle, and charging in the car only works if we’re flying near the car.

I wound up buying a big, honking 10,000 mAh 6S LiPo from Hobby King for $70. They have a lot of these big LiPos ranging from 10,000 mAh 3S to 20,000 mAh 6S. It seems like one size is always on sale.

This battery is big enough to charge a dozen of my 1300 mAh 5S packs, 16 or 17 1300 mAh 4S packs, or a seemingly infinite number of 3S micro quad batteries. These big field charging packs are only rated for 10C, but on a pack this big, that’s 100 amps. It has no trouble driving the ISDT charger at its maximum charging rate of 14 amps. We can parallel-charge six batteries in less than 25 minutes.

NOTE: I need to verify the math on the 1300 mAh 4S packs. It should be close.

Conclusion

I don’t want the worlds fastest racing quad. I don’t want to race at all. I want my quad to be powerful enough that I don’t notice the weight of a GoPro. I want my quad to have as much power available when it is time to land as it did when I plugged the battery in. My 5S quad with 2600 KV motors gives me all that.

I also don’t want to have to pay for premium batteries, because I damage them all the time. I can buy three China Hobby Line 5S LiPos for less than the price of two premium 4S LiPos.

If my experience so far is any indication, the future of miniquads is almost certainly 5S or 6S batteries. Are you running 5S or 6S? Tell us about your experience in the comments, or join our Discord server and tell us about it!